The present invention relates to a discharge device and a DC power supply system for preventing erroneous operation in a power supply stabilizer.
Nowadays, series regulators (power supply stabilizers) are often used to stabilize power supplies. When an input power supply voltage exceeds an activation voltage in these series regulators, a predetermined voltage is output from the output terminal. Normally, a stabilizing capacitor is arranged at the output terminal (for example, refer to Japanese Laid-Open Patent Publication No. 2004-129489). Then, when the input power supply voltage of the series regulator drops below the activation voltage, the series regulator stops operating.
When the input power supply voltage of the series regulator is higher than the series regulator activation voltage, the series regulator enters operates even when the input power supply voltage of the series regulator is less than the output power supply voltage. The charge accumulated in the stabilizing capacitor connected to the output side power supply terminal is supplied to each block connected to the output terminal as the regulator output.
Due to the stabilizing capacitor connected to the output terminal of the series regulator, when the input power supply voltage becomes lower than the activation voltage, output voltage is supplied from the series regulator due to the residual voltage that is still in the stabilizing capacitor. Therefore, there is a possibility of the series capacitor operating even through the blocks connected to the output terminal are expecting the operation to be stopped.
Furthermore, the series regulator operates when the input power supply voltage of the series regulator is lower than the output power supply voltage and higher than the series regulator activation voltage. Thus, residual charge accumulates in the stabilizing capacitor connected to the output side power supply terminal. The residual charge may produce load current that causes an erroneous operation.